Gelatin is a protein obtained by a treatment of animal-derived collagen with an acid or alkali and subsequent extraction and is a familiar material which is utilized in various fields, for example, is used as a gelling agent in food fields such as jelly, pharmaceutical fields, and the like and is also used in industrial uses such as adhesive and film fields. Of these various uses, highly purified gelatin and collagen used in medical uses are listed also in the Japanese Pharmacopoeia and have been widely utilized as an additive for injection preparations and in products such as an embolic material for liver cancer, a sponge material for hemostasis, and a capsule material for oral administration.
As mentioned above, since gelatin is extracted from collagen that constitutes biological tissues, gelatin is a material extremely excellent in biocompatibility and biodegradability. Furthermore, gelatin usually has a property of relatively easily dissolving in water and warm water and, by subjecting gelatin to a crosslinking treatment to thereby achieve insolubilization and controlling a degree of insolubilization, has a property that a biodegradation time of gelatin can be controlled at the time when it is administrated to a living body. Therefore, when a physiologically active substance such as a drug is previously adsorbed to a crosslinked and insolubilized gelatin, in the case where it is administrated to a living body, the physiologically active substance can be gradually released along with dissolution of gelatin by biodegradation, so that an action of controlled releasing of the physiologically active substance over a certain period of time can be exhibited.
Patent Document 1 discloses an invention in which gelatin as a biocompatible substance is made water-insoluble and is transformed into a porous particle and there is a description that the particle is useful for embolization treatment and as a support for medical preparations. Namely, the water-insolubilized porous particle is impregnated in its porous part with physiological saline or a solution of a pharmaceutical or the like and retains it. However, since the impregnation and retention are achieved in its porous part, for example, the adsorbed amount thereof is varied to a large extent when the pore diameter and the porosity are changed, so that there is a problem that it is difficult to control the adsorbed amount.
Patent Document 1: Japanese Patent No. 3879018